Utility systems, such as those serving a town or city, comprise a power grid having power lines for local distribution at a high voltage and this is in turn reduced to a lower voltage, usually 220V or 110V, for distribution to individual consumer facilities within a limited area served by a step-down utility power transformer. In many areas these transformers are located on power poles, and in others they are disposed on the ground or below ground. In a residential neighborhood, for example, one power transformer may serve several homes; whereas, in a commercial or industrial area there may be one or more transformers per business establishment.
The typical utility power transformer today comprises a case which houses the usual primary and secondary windings and conductors, and along with a transformer liquid or oil. Unfortunately, from time to time, these transformers leak because of rust or corrosion of the case, and the transformer oil flows from the transformer to the surrounding area. In those installations where the transformer is mounted on a power pole, frequently the oil leaks onto the pole or its cross members and may not significantly contaminate the ground below. On the other hand, where the transformer is disposed on the ground or below ground level, if such leaking occurs it contaminates the underlying and surrounding soil requiring clean-up of the soil.
In relatively hot areas, such as desert areas of Nevada, Arizona, and the like, the transformer leaking problem is more acute. In the Las Vegas, Nev. area for example, residential transformers usually are situated on the ground or below ground level, and when a leak occurs it is necessary to remove the transformer, clean up the underlying and surrounding soil, and then install a new transformer. This procedure involves disconnecting the electrical conductors of the faulty transformer and providing a temporary AC power source in the form of a portable motor-generator or alternator in place of the transformer while the soil is cleaned up. It is particularly necessary in hot geographical areas to do this because the residences or other buildings cannot be without cooling or air conditioning for the frequently prolonged period of soil clean-up. Needless to say, it is important to expeditiously and economically complete the change-out procedure.
Since the average power transformer change-out requires a temporary power supply typically of 67.5 KVA, the size of the portable motor-generator system and cost is a big concern. The initial cost for one such portable system is approximately $45,000, not to mention all of the other upkeep and on-going operating costs.
Accordingly, a need exists for a more efficient and economical system and method of change-out of leaking or other defective transformers.